Question

The size and sophistication of Native American civilizations in Mexico and South America can be attributed to

Answer 1

The correct option is D.
The development of agriculture opened the way of civilization for native Americans in Mexico and South America. The cultivation of maize in large quantity especially brought about trading with neighboring cities and towns and open up irrigation system and increased the population density of Mexico and South America.

Answer 2

Answers C and D seem to make the most sense. Between those two I would say letter D.